1. Field of the Invention
The invention relates to a part for connecting a fluid line to an opening of a container, comprised substantially of thermoplastic material, in particular, polyolefin, or for closing the opening, wherein the part comprises at least one first and second component primarily of thermoplastic material, wherein the material of the first component forms with the material of the container a heat fusion joint by welding but has no sufficient diffusion barrier capability relative to hydrocarbons, such as gasoline or diesel fuel, and wherein the material of the second component has a significantly higher diffusion barrier capability and reduced swelling capability relative to hydrocarbons and a higher mechanical strength, even after hydrocarbon exposure, as well as a higher thermal shape stability than the material of the first component.
2. Description of the Related Art
In a part of this kind known from DE 100 62 997 A1 in the form of a pipe-shaped socket, the first component comprises polyethylene (PE), in particular high-density polyethylene (HDPE), and the second component polyamide (PA). A section of the first component which is remote from the container to which the pipe socket is to be welded is surrounded by injection molding by the material of the second component. An annular part of the first component is welded to the container. The container is also comprised substantially of HDPE. Therefore, when welded, it forms a heat fusion connection with the first component. The polyamide of the second component has a high diffusion barrier capability and reduced swelling capability with regard to fuels, such as gasoline or diesel fuel, and, moreover, a high mechanical strength. In the section of the first component that is embedded by injection molding by the second component, the pipe socket is thus substantially impermeable relative to diffusion of fuels. Even though the materials of the two components in their overlap area form an intimate heat fusion connection by bridge formation, there may still be the situation that in the overlap area between the two components leakage occurs in that fuel escapes along the connecting surface of the components because the connecting surface is exposed directly to fuel across its inner edge and because it has the tendency to tear as a result of the higher swelling capability of the material of the first component in comparison to that of the second component. Moreover, the fuel can diffuse through the annular part.